As it was emphasized more recently in Refs. [1]}, [2]},
WZ terms
display an axion-like behaviour
(as can be understood by applying the equivalence theorem to the longitudinal component of \(\mathcal {X}\) )
and lead to amplitudes that grow with the energy.
The anomalous \(\mathcal {X}W \partial W\)  vertex can be dressed with SM flavour-violating
interactions leading to loop-induced flavour changing neutral current (FCNC) processes,
while the anomalous \(\mathcal {X}B \partial B\)  vertex is responsible for
\(Z \rightarrow \gamma \mathcal {X}\)  decays at the tree level (see also [3]}, [4]}, [5]}, [6]}).
In both cases these processes
are enhanced as \((\text{energy} / m_{\mathcal {X}})^2\) , thus
resulting into the typically most stringent bounds on light vectors
with no direct couplings to electrons,
as e.g. in the case of gauged baryon number.
